Higher-order Mode Effects on Seismic Performance of Tall Piers

A comprehensive analysis was conducted for the investigation of seismic performance of a typical tall bridge pier through dynamical incremental analysis (IDA), in which the effect of higher-order modes was emphatically studied. The results show that higher order modes contributed a lot to the structural seismic response and should not be neglected. It resulted in an additional hinge at the middle height where it is usually regarded no plastic hinge would occur for conventional bridge piers. Higher order modes also led to out of phase response between the hinge rotation at the pier bottom and the displacement at the top. This causes the displacement based seismic design method can’t correctly predict the mechanical state of the critical hinge and therefore not suitable for the seismic design of tall piers, or a seriously unsafe error may be resulted in.